1. Field of the Invention
This invention pertains to devices used to lift concrete building or retaining wall blocks in position on a wall, and more particularly, to such devices that enable the blocks to be lifted directly from their pallets and easily repositioned for placement on the wall.
2. Description of the Related Art
Lifting devices that are attachable to backhoes to help construction workers more efficiently set concrete blocks in place on building or retaining walls are widely known. These devices eliminate the need for workers to individually lift and position the heavy concrete blocks, saving time, physical energy, and labor cost. Unfortunately, such devices are able to lift and position only one concrete block at a time, which makes wall building a slow, tedious process.
Retaining wall blocks are shipped from the manufacturer on pallets. Typically, the concrete blocks are stacked in layers on the pallet 97 five to six blocks high with the concrete blocks 12, 12,xe2x80x2, 12xe2x80x3 in each layer being arranged side-by-side in two, opposite aligned triangular configurations, as shown in FIG. 3. Because each block has one or two centrally located holes 91, 92, formed therein and typically weighs approximately 120 lbs, heavy equipment, such as a tractor or backhoe, is normally used to individually lift each concrete block from the pallet and then rotate it for proper placement on the wall.
In order to expedite the process and reduce labor and equipment rental costs, what is needed is a lifting device that can easily and securely attach to a plurality of concrete blocks on a pallet, rotate them for proper placement on a wall, and then easily release them directly off the shipment pallet.
It is an object of the present invention to provide a device that easily and securely lifts a plurality of concrete blocks using common construction lifting equipment, such as a tractor, backhoe or forklift.
It is another object of the present invention to provide such a device that lifts the concrete blocks in the original positions on a shipping pallet.
It is a further object of the invention to provide such a device that allows the user to readjust the relative positions of the lifted concrete blocks for proper alignment on a wall.
These and other objects of the invention which will become apparent are met by the lifting device disclosed herein that includes a main clamping member that selectively attaches to one concrete block on the pallet and at least one movable side clamping member that selectively attaches to a second concrete block located on the same layer of concrete blocks on the pallet. After both clamping members are attached to the concrete blocks, the lifting device is lifted by suitable lifting equipment until they clear other remaining concrete blocks on the pallet. The side clamping member is then moved relative to the main clamping member so that the two concrete blocks are aligned side by side so that the front faces of the blocks are longitudinally aligned for placement on a straight or slightly curved wall. When the concrete blocks are lifted and properly positioned over the wall, the lifting device is lowered until the concrete blocks are positioned above the desired locations and then selectively released from the main and side clamping members. The lifting device is then returned to the pallet to pick up other concrete blocks.
In the preferred embodiment, the lifting device is designed to lift three concrete blocks located in one layer and oriented in the same direction and in a triangular configuration, as shown in FIG. 3. The lifting device includes one fixed main clamping member and two rotating side clamping members mounted on the ends of two pivoting arms. The relative locations of the main clamping member and the two side clamping members, and the length of the two arms are sufficient so that triangularly configured concrete blocks located in a layer on a pallet may be engaged and lifted. During operation, each arm is selectively pivoted from a forward, laterally extended position to a rearward, laterally extended position. When the arms are aligned in a forward laterally extended position, the three clamping members may attach to three concrete blocks aligned in a triangular configuration on the pallet. When the arms are lifted and pivoted into a rearward, laterally extended position, the side clamping members are automatically rotated so that the front faces of the blocks are side by side and linearly configured. The blocks are then longitudinally aligned for immediate placement on a wall. Each side arm includes a linking arm that connects each side clamping member with the main frame member so that when the arm is pivoted, the side clamping member automatically rotates thereby keeping the side clamping member and main clamping member facing the same direction.
The lifting device also includes an eye bolt or hook connected to the main frame member which connects to a chain or cable attached to a backhoe or forklift which is used to lift the lifting device and position the blocks on the wall.
In one embodiment, movement of the arms and control of the main and side clamping members are simultaneously coordinated and controlled by a hydraulic control system that connects to the hydraulic system used on the backhoe or tractor. In another embodiment, no control system is provided so that the movements of the arms are manually controlled and the blocks are automatically engaged whenever the clamping members are inserted into one of the holes on the blocks and an upward lifting force is applied thereto. A manual lever is then used to temporarily disengage the clamping members from the blocks so that the lifting device may be lifted away.
The lifting device includes an optional arc adjustment means that enables the user to selectively adjust the amount of rotation of each arm relative to the main clamping member so that the device may be used with different sized concrete blocks originally positioned in a triangular configuration on a pallet.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto.